There are different versions of Tableau.
You can download Tableau Public or obtain a one year Tableau student license. Faculty can obtain a Tableau license for teaching.
Register an account with Tableau, and watch this videos to get started.
You also need to prepare your data into a format that Tableau could process. Read tips for working with your data. To learn more on how to structure your data, read get your data Tableau ready.
For your assignment, you need to connect the return data with order data by matching order IDs. Tableau has a join function to make this work. To learn more about join, take a look at this Join Your Data page.
Here are a list of functions you might need to finish your assignment. Read the following pages if you need to learn more after class.
Create parameters, especially swap measures using parameters
Functions, pay attention to the COUNTD function
Before you publish your visualizations, you can create either a dashboard or a storyboard. The dashboard is to have visualizations on one canvas, while storyboard looks like a photo book that you can flip.
To learn more, watch the videos on dashboards and stories.
Once everything is ready, you can publish to Tableau online. Watch the video on publishing and embedding vizzes.
Remember, you can only publish visualizations you created using public dataset. Do not publish something you created using data that is not publicly available. You can also disable data download so that people can only download your visualizations, but not your raw data.